Quantum dots(QDs) are great interest in past decade, due to their unique, tunable optical properties. Luminescent QDs exhibit high photoluminescence quantum yield, large extinction coefficients, and strong resistance to photo- and chemical degradation. For highest quality QDs, QDs are synthesized by pyrolysis method in organic media. In this condition, QDs is capped with hydrophobic ligand which cannot give colloidal stability in water to QDs. So, ligand exchange with hydrophilic ligands is the essential step for biological application of QDs. In this research, ligands containing primary, tertiary amine group and zwitterion are synthesized based on lipoic acid. Primary amine group is used to react with biomolecule such as streptavidin via EDC coupling. Tertiary amine group and zwitterion give QDs to a colloidal stability in various water solutions. The ligand exchange with controlling ratio between reactive group and stabilizing group, we can make easily surface modified QDs which are well dispersed to broad pH range and high ionic strength water conditions. Therefore these QDs have colloidal stability at conjugation buffer condition, we make QD ？ biomolecule conjugates without aggregation via EDC coupling. These QDs ？ biomolecule conjugates will be using bioactive fluorescent probes. Characterization of surface modified QDs is done by optical spectroscopy and dynamic light scattering.